The present invention relates to methods and compositions for the treatment of diseases, including cancer, infectious diseases and autoimmune diseases. The present invention also relates to methods and compositions for improving immune function. More particularly, the present invention relates to multifunctional molecules that are capable of being delivered to cells of interest for the treatment of diseases and for the improvement in immune function.
The publications and other materials used herein to illuminate the background of the invention, and in particular, cases to provide additional details respecting the practice, are incorporated by reference, and for convenience are referenced in the following text by author and date and are listed alphabetically by author in the appended bibliography.
Signal Transducer and Activator of Transcription 3 (Stat3) is constitutively activated at high frequency (50 to 100%) in diverse cancers (Yu and Jove, 2004; Yu et al., 2007; Kortylewski et al., 2005a). Blocking Stat3 in tumor cells induces tumor cell apoptosis, inhibits tumor angiogenesis and abrogates metastasis (Yu and Jove, 2004; Yu et al., 2007; Xie et al., 2004; Xie et al., 2006), and activates antitumor immune responses (Wang et al., 2004; Kortylewski et al., 2005b). Our recent studies further demonstrate that Stat3 is constitutively activated in tumor-stromal myeloid cells, including Gr1+ immature myeloid cells, DCs, macrophages, NK cell, neutrophils. Activated Stat3 inhibits expression of Th-1 type immune responses while promoting tumor accumulation of T regulatory cells and Th17 cells, compromising antitumor effects of immune effector cells, such as NK cells, neutrophils and CD8+ T cells (Kortylewski et al., 2005b). Blocking Stat3 in the immune subsets leads to activation of antitumor immunity and immune-mediated tumor growth inhibition and tumor regression (Kortylewski et al., 2005b). Our preliminary data further demonstrate that Stat3 is constitutively activated in CD4+CD25−/Foxp3+ T regulatory cells within the tumor stroma. A requirement of Stat3 for expression of Foxp3, TGFβ and IL-10—the hallmarks of T regulatory cells—in CD4+ T cells has been demonstrated in both animal models and human T cells obtained from clinical trials (Yu et al., 2007). A recent study involving human melanoma cells has also confirmed a critical role of Stat3 in mediating tumor immune evasion/suppression (Sumimoto et al., 2006).
Stat3 is a point of convergence for numerous tyrosine kinase signaling pathways, which are the most frequently overactive oncogenic pathways in tumor cells of diverse origins (Yu and Jove, 2004). The reason Stat3 is also constitutively-activated in tumor stromal cells is because many of the Stat3 target genes encode secreted molecules whose cognate receptors signal through Stat3 (Yu et al., 2007). For example, Stat3-regulated products such as IL-10, IL-6 and VEGF have their receptors in diverse myeloid cells and T lymphocytes. VEGF and bFGF, both of which also require Stat3 for their expression, activates Stat3 in endothelial cells. Activated Stat3 promotes expression of a wide range of genes critical for tumor cell survival, proliferation, angiogenesis/metastasis and immune suppression. Activated Stat3 also inhibits expression multiple genes that are pro-apoptotic, anti-angiogenic and Th-1 type immunostimulatory, whose upregulation are critical for anti-cancer therapy (Yu and Jove, 2004; Yu et al., 2007; Kortylewski et al., 2005b).
RNA interference provides compelling opportunities to control gene expression in cells and siRNAs therefore represent a family of new drugs with broad potential for the treatment of diverse human diseases. Several recent studies have demonstrated the feasibility of in vivo siRNA delivery, leading to therapeutic effects in mouse models (Song et al., 2005; Hu-Lieskovan et al., 2005; McNamara et al., 2006; Kumar et al., 2007; Poeck et al., 2008) and also in non-human-primates (Li et al., 2005; Zimmermann et al., 2006). Nevertheless, efficient in vivo targeted delivery of siRNA into specific cell types, especially those of immune origin, which are important constituents of the tumor microenvironment and active players in promoting tumor progression, remains to be fully explored before the full potential of therapeutic RNA interference can be realized. One promising approach for targeted delivery of siRNA is the use of aptamers, which are oligonucleotide-based ligands that bind to specific receptors, such as those on tumor cells (McNamara et al., 2006). Recent studies further indicated the ability of specific aptamers to bind and modulate the functions of their cognate targets in T cells, leading to potent antitumor immune responses (McNamara et al., 2008). However, whether these aptamers can mediate siRNA delivery into T cells remains to be determined.
The immune system can serve as extrinsic tumor suppressor (Bui and Schreiber, 2007; Koebel et al., 2007; Shankaran et al., 2001). However, the microenvironment of established tumors is typically characterized by a paucity of tumor-specific CD8+ T cells together with an excess of suppressive regulatory T cells and myeloid-derived suppressor cells (MDSC) that promote tumor immune evasion (Kortylewski et al., 2005b; Yu et al., 2005; Curiel et al., 2004; Ghiringhelli et al., 2005; Melani et al., 2003). Myeloid cells and other immune cells in the tumor microenvironment also produce growth factors and angiogenic/metastatic factors critical for tumor progression (Kujawski et al., 2008). As noted above, Stat3 is an important oncogenic molecule. The orchestration of these processes in the tumor microenvironment is highly dependent on the oncogenic transcription factor, Stat3 (Yu et al., 1995; Bromberg et al., 1999; Yu and Jove, 2004; Darnell, 2002; Yu et al., 2007). In particular, we and others have recently demonstrated a critical role of Stat3 in mediating tumor immune evasion (Wang et al., 2004; Kortylewski et al. 2005b; Yu et al., 2007). Activated Stat3 in myeloid cells inhibits expression of a large number of immunostimulatory molecules related to Th1-type responses, while promoting production of several key immunosuppressive factors (Yu et al., 2007, Kortylewski and Yu, 2008; Kortylewski et al., 2009a) as well as angiogenic factors (Kujawski et al., 2008). In addition, by mediating signaling of certain cytokines and growth factors, notably IL-6, Stat3 activation in myeloid cells activates Stat3 in tumor cells, enhancing tumor cell proliferation and survival (Bollrath et al., 2009; Grivennikov et al., 2009; Lee et al., 2009; Wang et al., 2009).
It is desired to develop new molecules and methods for the treatment of cancer and other diseases, including new molecules and methods for treatment that involve pathways within cells that modulate the disease, such as the Stat3 pathway.